Ionization of light atoms by ultra-fast ions

We propose a semi-relativistic symmetric eikonal distorted wave method (SRSE) for treating collisions of fast and ultra-fast projectiles with light and medium-heavy atomic targets. The projectile interaction with target electrons is described by the Liénard-Wiechert (LW) potential, within the impact parameter approach. Our model allows to estimate two-centre effects in fast heavy-particle collisions and analyse the limit of the ultra-relativistic collisions. We show that the improvement upon the first Born approximation (FBA) by taking into account the exact boundary conditions in the entrance and exit channels eliminates the well-known anomaly of the FBA ionization cross section at ultra-relativistic impact velocities.